DAMASCUS, May 25 -- At least 35 people were killed Thursday by U.S.-led airstrikes on areas in eastern Syria, a monitor group reported.

The airstrikes targeted areas under the control of the Islamic State (IS) group in the city of Mayadeen in the countryside of Deir al-Zour province, said the Syrian Observatory for Human Rights.

A day earlier, the Observatory said that 16 civilians were killed by U.S.-led strikes on the northern city of Raqqa, the de facto capital of IS, just hours after 15 civilians got killed as a result of explosions of mines in Raqqs countryside.

Raqqa and Deir al-Zour have been the target of the U.S.-led coalition, which is backing the Kurdish-led Syrian Democratic Forces (SDF) in their push against IS in Raqqa countryside and areas near Deir al-Zour.

As a result, civilian casualties have become falling on a higher rate recently with reports of civilian deaths due to the intensification of U.S.-led strikes.